Sam Underhill turned from hero to villain for Bath Rugby on Sunday as he conceded a late penalty to allow Fin Smith to kick an 80th minute match-winning penalty to hand Northampton Saints a 35-34 victory at Franklin's Gardens to keep the hosts alive in the race for Gallagher Premiership play-offs.

Underhill had come off the bench in the first half to help turn around Bath's display around after the hosts went 19 points down in the first quarter, but the England star failed to listen to referee Anthony Woodthorpe's instructions to leave the ball at the ruck in the final seconds of the game and paid a heavy price in a pulsating Premiership classic which saw nine tries scored.

It was Bath’s fifth consecutive loss at Franklin’s Gardens, but the league leaders showed remarkable resilience to lead with three minutes to go and outscore their opponents by five tries to four. Joe Cokanasiga scored two tries with Orlando Bailey, Will Stuart and Max Ojomoh also on the scoresheet as Finn Russell converted three and adding a penalty. George Hendy, Fraser Dingwall, James Ramm and Josh Kemeny scored Saints’ tries, with Smith kicking three conversions and three penalties.

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England wing Ollie Sleightholme withdrew from Saints’ bench with a hamstring problem, but soon overcame the setback to take the lead after only 79 seconds. Hendy secured the kick-off to secure an attacking platform before he and Rory Hutchinson combined neatly down the right flank to create a try for Kemeny.

Bath soon suffered two further blows in quick succession. Flanker Guy Pepper was forced to leave the field with a leg injury before creative play from half-backs Smith and Alex Mitchell set up a walk-in for Dingwall. Saints’ explosive start continued with a third try before 13 minutes had elapsed as Ramm powered through the visitors’ defence on a 50-metre run to the line.

Bath needed a quick response and they got one when skilful passing from their backs provided Cokanasiga to round Hendy and score.

Aided by a number of penalties in their favour, Bath built up their first sustained period of pressure and were rewarded when Bailey brushed aside some weak defending for his side’s second score after running onto a peach of a pass from Russell.

A sixth match try came before the half-hour with Hendy collecting Smith’s chip ahead for Saints’ bonus-point before Will Muir departed with a leg injury which forced flanker Josh Bayliss to play on the wing as Bath had selected only one back on the bench.

Just before the interval, the hosts lost the impressive Hendy with an injured shoulder, but they still led 26-12 at half-time.

Six minutes after the restart, Bath were right back in contention when Stuart crashed over from close-range, but Smith was on target with a penalty to keep the visitors temporarily at arms length.

However, Ojomoh scored Bath’s bonus-point try to reward a strong burst from Ollie Lawrence to close the visitors within three points going into the final quarter.

Bath then lost a badly-shaken Jaco Coetzee following a head-on-head collision, but they still took the lead for the first time when Miles Reid charged down a kick from Hutchinson for Cokanasiga to gather and outpace the defence from 40m out.

Russell missed the conversion as did Smith with a penalty, but the young outside-half put Saints back in front with 10 minutes remaining with a 40-metre kick. Smith then missed with a penalty from inside his own half before Alex Mitchell was sin binned for a high tackle on Lawrence with Russell knocking over the kick, but Smith had the final say when Underhill offended.

Northampton Saints: 15. George Hendy, 14. Tommy Freeman, 13. Fraser Dingwall (c), 12. Rory Hutchinson, 11. James Ramm, 10. Fin Smith, 9. Alex Mitchell; 1. Tom West, 2. Curtis Langdon, 3. Trevor Davison, 4. Temo Mayanavanua, 5. Alex Coles, 6. Josh Kemeny, 7. Tom Pearson, 8. Juarno Augustus

Replacements: 16. Henry Walker, 17. Tarek Haffar, 18. Luke Green, 19. Tom Lockett, 20. Henry Pollock, 21. Angus Scott-Young, 22. Archie McParland, 23. Ollie Sleightholme

Bath Rugby: 15 Orlando Bailey, 14 Joe Cokanasiga, 13 Ollie Lawrence, 12 Max Ojomoh, 11 Will Muir, 10 Finn Russell, 9 Ben Spencer; 1 Beno Obano, 2 Tom Dunn, 3 Will Stuart, 4 Quinn Roux, 5 Ross Molony, 6 Guy Pepper, 7 Miles Reid, 8 Alfie Barbeary

Replacements: 16 Kepu Tuipulotu, 17 Francois van Wyk, 18 Thomas du Toit, 19 Charlie Ewels, 20 Sam Underhill, 21 Louis Schreuder, 22 Josh Bayliss, 23 Jaco Coetzee.

Referee: Anthony Woodthorpe (37th game)

Assistant Referees: Daniel Jones & Calum Howard

TMO: Stuart Terheege